The applicants propose that the overall goal of the proposed NIDDM Primary Prevention Trial should be to prevent the development or progression of early NIDDM in high risk volunteers with IGT or a prior history of gestational diabetes mellitus (GDM) by correcting behaviors thought responsible for the increase in NIDDM. The proposed intervention is centered on an intensive, multi-disciplinary, program to promote long-term weight loss and increased physical activity among 200 volunteers who work in or live near the Washington University Medical Center in St. Louis. The proposed intervention is designed to minimize physical discomfort and life style disruption, to emphasize gradual, moderate changes in the foods usually eaten, to maximize continued adherence over five years and to be acceptable to both white and African American volunteers. In order to sustain this weight loss long term, it is proposed to have the intensively managed patients seen regularly by trained members of a multidisciplinary team that will consist of an exercise technician, a nutritionist, a nurse, and a social worker trained in behavioral medicine. Volunteers randomized to the control group will be seen quarterly and provided with state of the art educational and motivational materials that will include recommendations for weight loss, increased physical activity aid a prudent diet low in saturated fats and cholesterol. Three first stage studies are proposed for high risk white and African American volunteers. The NIDDM Primary Prevention Study, will compare rates of conversion from persistent IGT to persistent, mild NIDDM (defined operationally as patients with fasting plasma glucoses less than 140 mg/dl and both one and two hour values above 200 mg/dl) and improvement to normal glucose tolerance. The NIDDM Early Intervention Study, will examine the effects of the intensive intervention on patients found during screening to have mild NIDDM. The third, GDM Primary Prevention Study, will compare rates of progression from normal glucose tolerance to IGT or NIDDM in women with previous GDM. A single, second stage, intervention is proposed for volunteers who proceed to develop sustained fasting glucoses> 140 mg/dl. These patients will remain in their original treatment assignment (i.e. intensive or conventional treatment) for the duration of the Trial but will be randomly assigned to one of two drug treatment protocols to be chosen by early 1995 during the design of the trial.